<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      html,
      body {
        margin: 0;
        padding: 0;
      }

      button {
        margin: 0;
        padding: 0;
        border: 0;
        background: none;
        font-size: 100%;
        vertical-align: baseline;
        font-family: inherit;
        font-weight: inherit;
        color: inherit;
        -webkit-appearance: none;
        appearance: none;
        -webkit-font-smoothing: antialiased;
        -moz-osx-font-smoothing: grayscale;
      }

      body {
        font: 14px "Helvetica Neue", Helvetica, Arial, sans-serif;
        line-height: 1.4em;
        background: #f5f5f5;
        color: #111111;
        min-width: 230px;
        max-width: 550px;
        margin: 0 auto;
        -webkit-font-smoothing: antialiased;
        -moz-osx-font-smoothing: grayscale;
        font-weight: 300;
      }

      :focus {
        outline: 0;
      }

      .hidden {
        display: none;
      }

      .todoapp {
        background: #fff;
        margin: 130px 0 40px 0;
        position: relative;
        box-shadow: 0 2px 4px 0 rgba(0, 0, 0, 0.2),
          0 25px 50px 0 rgba(0, 0, 0, 0.1);
      }

      .todoapp input::-webkit-input-placeholder {
        font-style: italic;
        font-weight: 300;
        color: rgba(0, 0, 0, 0.4);
      }

      .todoapp input::-moz-placeholder {
        font-style: italic;
        font-weight: 300;
        color: rgba(0, 0, 0, 0.4);
      }

      .todoapp input::input-placeholder {
        font-style: italic;
        font-weight: 300;
        color: rgba(0, 0, 0, 0.4);
      }

      .todoapp h1 {
        position: absolute;
        top: -140px;
        width: 100%;
        font-size: 80px;
        font-weight: 200;
        text-align: center;
        color: #b83f45;
        -webkit-text-rendering: optimizeLegibility;
        -moz-text-rendering: optimizeLegibility;
        text-rendering: optimizeLegibility;
      }

      .new-todo,
      .edit {
        position: relative;
        margin: 0;
        width: 100%;
        font-size: 24px;
        font-family: inherit;
        font-weight: inherit;
        line-height: 1.4em;
        color: inherit;
        padding: 6px;
        border: 1px solid #999;
        box-shadow: inset 0 -1px 5px 0 rgba(0, 0, 0, 0.2);
        box-sizing: border-box;
        -webkit-font-smoothing: antialiased;
        -moz-osx-font-smoothing: grayscale;
      }

      .new-todo {
        padding: 16px 16px 16px 60px;
        border: none;
        background: rgba(0, 0, 0, 0.003);
        box-shadow: inset 0 -2px 1px rgba(0, 0, 0, 0.03);
      }

      .main {
        position: relative;
        z-index: 2;
        border-top: 1px solid #e6e6e6;
      }

      .toggle-all {
        width: 1px;
        height: 1px;
        border: none; /* Mobile Safari */
        opacity: 0;
        position: absolute;
        right: 100%;
        bottom: 100%;
      }

      .toggle-all + label {
        width: 60px;
        height: 34px;
        font-size: 0;
        position: absolute;
        top: -52px;
        left: -13px;
        -webkit-transform: rotate(90deg);
        transform: rotate(90deg);
      }

      .toggle-all + label:before {
        content: "❯";
        font-size: 22px;
        color: #e6e6e6;
        padding: 10px 27px 10px 27px;
      }

      .toggle-all:checked + label:before {
        color: #737373;
      }

      .todo-list {
        margin: 0;
        padding: 0;
        list-style: none;
      }

      .todo-list li {
        position: relative;
        font-size: 24px;
        border-bottom: 1px solid #ededed;
      }

      .todo-list li:last-child {
        border-bottom: none;
      }

      .todo-list li.editing {
        border-bottom: none;
        padding: 0;
      }

      .todo-list li.editing .edit {
        display: block;
        width: calc(100% - 43px);
        padding: 12px 16px;
        margin: 0 0 0 43px;
      }

      .todo-list li.editing .view {
        display: none;
      }

      .todo-list li .toggle {
        text-align: center;
        width: 40px;
        /* auto, since non-WebKit browsers doesn't support input styling */
        height: auto;
        position: absolute;
        top: 0;
        bottom: 0;
        margin: auto 0;
        border: none; /* Mobile Safari */
        -webkit-appearance: none;
        appearance: none;
      }

      .todo-list li .toggle {
        opacity: 0;
      }

      .todo-list li .toggle + label {
        /*
		Firefox requires `#` to be escaped - https://bugzilla.mozilla.org/show_bug.cgi?id=922433
		IE and Edge requires *everything* to be escaped to render, so we do that instead of just the `#` - https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/7157459/
	*/
        background-image: url("data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%22http%3A//www.w3.org/2000/svg%22%20width%3D%2240%22%20height%3D%2240%22%20viewBox%3D%22-10%20-18%20100%20135%22%3E%3Ccircle%20cx%3D%2250%22%20cy%3D%2250%22%20r%3D%2250%22%20fill%3D%22none%22%20stroke%3D%22%23ededed%22%20stroke-width%3D%223%22/%3E%3C/svg%3E");
        background-repeat: no-repeat;
        background-position: center left;
      }

      .todo-list li .toggle:checked + label {
        background-image: url("data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%22http%3A//www.w3.org/2000/svg%22%20width%3D%2240%22%20height%3D%2240%22%20viewBox%3D%22-10%20-18%20100%20135%22%3E%3Ccircle%20cx%3D%2250%22%20cy%3D%2250%22%20r%3D%2250%22%20fill%3D%22none%22%20stroke%3D%22%23bddad5%22%20stroke-width%3D%223%22/%3E%3Cpath%20fill%3D%22%235dc2af%22%20d%3D%22M72%2025L42%2071%2027%2056l-4%204%2020%2020%2034-52z%22/%3E%3C/svg%3E");
      }

      .todo-list li label {
        word-break: break-all;
        padding: 15px 15px 15px 60px;
        display: block;
        line-height: 1.2;
        transition: color 0.4s;
        font-weight: 400;
        color: #4d4d4d;
      }

      .todo-list li.completed label {
        color: #cdcdcd;
        text-decoration: line-through;
      }

      .todo-list li .destroy {
        display: none;
        position: absolute;
        top: 0;
        right: 10px;
        bottom: 0;
        width: 40px;
        height: 40px;
        margin: auto 0;
        font-size: 30px;
        color: #cc9a9a;
        margin-bottom: 11px;
        transition: color 0.2s ease-out;
      }

      .todo-list li .destroy:hover {
        color: #af5b5e;
      }

      .todo-list li .destroy:after {
        content: "×";
      }

      .todo-list li:hover .destroy {
        display: block;
      }

      .todo-list li .edit {
        display: none;
      }

      .todo-list li.editing:last-child {
        margin-bottom: -1px;
      }

      .footer {
        padding: 10px 15px;
        height: 20px;
        text-align: center;
        font-size: 15px;
        border-top: 1px solid #e6e6e6;
      }

      .footer:before {
        content: "";
        position: absolute;
        right: 0;
        bottom: 0;
        left: 0;
        height: 50px;
        overflow: hidden;
        box-shadow: 0 1px 1px rgba(0, 0, 0, 0.2), 0 8px 0 -3px #f6f6f6,
          0 9px 1px -3px rgba(0, 0, 0, 0.2), 0 16px 0 -6px #f6f6f6,
          0 17px 2px -6px rgba(0, 0, 0, 0.2);
      }

      .todo-count {
        float: left;
        text-align: left;
      }

      .todo-count strong {
        font-weight: 300;
      }

      .filters {
        margin: 0;
        padding: 0;
        list-style: none;
        position: absolute;
        right: 0;
        left: 0;
      }

      .filters li {
        display: inline;
      }

      .filters li button {
        color: inherit;
        margin: 3px;
        padding: 3px 7px;
        text-decoration: none;
        border: 1px solid transparent;
        border-radius: 3px;
      }

      .filters li a:hover {
        border-color: rgba(175, 47, 47, 0.1);
      }

      .filters li a.selected {
        border-color: rgba(175, 47, 47, 0.2);
      }

      .clear-completed,
      html .clear-completed:active {
        float: right;
        position: relative;
        line-height: 20px;
        text-decoration: none;
        cursor: pointer;
      }

      .clear-completed:hover {
        text-decoration: underline;
      }

      .info {
        margin: 65px auto 0;
        color: #4d4d4d;
        font-size: 11px;
        text-shadow: 0 1px 0 rgba(255, 255, 255, 0.5);
        text-align: center;
      }

      .info p {
        line-height: 1;
      }

      .info a {
        color: inherit;
        text-decoration: none;
        font-weight: 400;
      }

      .info a:hover {
        text-decoration: underline;
      }

      /*
	Hack to remove background from Mobile Safari.
	Can't use it globally since it destroys checkboxes in Firefox
*/
      @media screen and (-webkit-min-device-pixel-ratio: 0) {
        .toggle-all,
        .todo-list li .toggle {
          background: none;
        }

        .todo-list li .toggle {
          height: 40px;
        }
      }

      @media (max-width: 430px) {
        .footer {
          height: 50px;
        }

        .filters {
          bottom: 10px;
        }
      }
    </style>
    <script src="https://unpkg.com/vue@next"></script>
  </head>
  <body>
    <div id="root"></div>
    <script>
     //1.添加代办事项
     function useAdd(todos) {
        const { ref } = Vue;
        const input = ref("");
        const addTodo = () => {
          const text = input.value;
          if (text.length === 0) return;
          todos.value.unshift({ text, completed: false });
          input.value = "";
        };

        return { input, addTodo };
      }

      //2.删除待办事项
      function useremove(todos) {
        const remove = (item) => {
          const index = todos.value.indexOf(item);
          todos.value.splice(index, 1);
        };
        const removeCompleted = () => {
          todos.value = todos.value.filter((todo) => !todo.completed);
        };
        return { remove, removeCompleted };
      }

      //3.切换待办事项
      function useFilter(todos) {
        const { computed, ref } = Vue;
        const allDown = computed({
          get() {
            return !todos.value.filter((todo) => !todo.completed).length;
          },
          set(value) {
            todos.value.forEach((todo) => {
              todo.completed = value;
            });
          },
        });

        const filter = {
          all: (list) => list,
          active: (list) => list.filter((todo) => !todo.completed),
          computed: (list) => list.filter((todo) => todo.completed),
        };

        const type = ref("all");
        const filterTodos = computed(() => filter[type.value](todos.value));
        const remainingCount = computed(
          () => filter.active(todos.value).length
        );
        const count = computed(() => todos.value.length);

        const handleChange = (item) => {
          type.value = item;
        };

        return { allDown, filterTodos, handleChange, remainingCount, count };
      }

      
      const app = Vue.createApp({
        setup() {
          const { ref } = Vue;
          const todos = ref([]);
          const { input, addTodo } = useAdd(todos);
          const { remove, removeCompleted } = useremove(todos);
          const { allDown, filterTodos, handleChange, remainingCount, count } =
            useFilter(todos);

          return {
            input,
            remove,
            addTodo,
            todos,
            allDown,
            filterTodos,
            handleChange,
            remainingCount,
            removeCompleted,
            count,
          };
        },
        template: `
          <header class="header">
            <h1>todos</h1>
            <input
            v-model="input"
            @keyup.enter="addTodo"
            type="text" class="new-todo" 
            placeholder="What needs to be done?" autocomplete="off" autofocus />
          </header>
          <section class="main" v-show="count">
            <input id="toggle-all" class="toggle-all" type="checkbox" v-model="allDown">
            <label for="toggle-all">Mark all as complete</label>
            <ul class="todo-list">
              <li v-for="item in filterTodos" >
                <div class="view">
                  <input type="checkbox" class="toggle" v-model="item.completed">
                   <label>{{item.text}}</label>
                  <button class="destroy" @click="remove(item)"></button>
                </div>
              </li>
            </ul>
          </section>
          <footer class="footer" v-show="count" >
            <span class="todo-count">
              <strong>{{remainingCount}}</strong> item left
            </span>
            <ul class="filters">
              <li><button @click="handleChange('all')">All</button></li>
              <li><button @click="handleChange('active')">Active</button></li>
              <li><button @click="handleChange('computed')">Completed</button></li>
            </ul>
            <button class="clear-completed" 
              v-show="count>remainingCount"
              @click="removeCompleted"> Clear completed</button>
          </footer>`,
      });

      app.directive("editing-focus", (el, binding) => {
        // el 就是节点
        binding.value && el.focus();
      });
      
      const vm = app.mount("#root");
    </script>
  </body>
</html>
